Heat pump type air conditioning system for automotive vehicle

ABSTRACT

A heat pump type air conditioning system (A) for an automotive vehicle. The heat type air conditioning system (A) comprises a first unit ( 10 ) including a heater core ( 11 ) through which an engine coolant of an engine flows, and a first heat exchanger ( 12 ) which forms part of a refrigeration cycle including a compressor ( 1 ) and a first condenser ( 3 ), in which a refrigerant circulates in the refrigeration cycle. A second unit ( 20 ) is provided including a second condenser ( 21 ) and a second heat exchanger ( 22 ) which are fluidly connected in parallel with the first heat exchanger ( 12 ). A valve (V 2 ) is fluidly connected in series with the second condenser ( 21 ) and disposed such that a part of the refrigerant is introduced through the valve into the second condenser ( 21 ) and the second heat exchanger ( 22 ). A sub-heat exchanger ( 30 ) is disposed outside the first and second units and fluidly connected in series with the second heat exchanger ( 22 ), in which the refrigerant flowing from the second heat exchanger ( 22 ) is introduced into the sub-heat exchanger to be heated by a part of the engine coolant, the refrigerant discharged from the sub-heat exchanger being returned to the compressor. An electromagnetic clutch ( 40 ) is provided such that the compressor ( 1 ) is drivably connectable with the engine therethrough. The electromagnetic clutch is engaged to establish a driving connection between the compressor so as to operate the compressor and disengaged to cut the driving connection so as to make the compressor inoperative. A control device (C) is operatively connected to the electromagnetic clutch ( 40 ) for controlling the electromagnetic clutch to be disengageable in accordance with a temperature within the air conditioning system (A).

This is a division of application Ser. No. 08/970,806, filed Nov. 14,1997 now U.S. Pat. No. 6,125,643.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improvements in a heat pump type airconditioning system for an automotive vehicle in which a passengercompartment is heated and refrigerated under the action of enginecoolant and refrigerant, and more particularly to the improvements tosolve various problems encountered in conventional similar heat pumptype air conditioning systems so as to offer the heat pump type airconditioning system suitable for practical use.

2. Description of the Prior Art

Hitherto, heat pump type air conditioning systems have been developedfor automotive vehicles. Such air conditioning systems carry out bothrefrigeration and heating for a passenger compartment under cycleoperations using a refrigerant. The air conditioning systems include asub-condenser or interior heat exchanger disposed inside the passengercompartment, in which high temperature and pressure refrigerant from acompressor is introduced into the sub-condenser so as to be used as aheat source for heating the passenger compartment. A main condenser orexterior heat exchanger is disposed outside the passenger compartment.Additionally, a four-way valve is provided to change over flow of therefrigerant from the sub-condenser to the main condenser and vise versato accomplish a changeover between a refrigeration operation and aheating operation of the air conditioning system. More specifically, therefrigerant discharged from the compressor is introduced to the maincondenser during the refrigeration operation, whereas the refrigerant isdirectly introduced to the sub-condenser through a bypass passage whichis formed bypassing the main condenser.

Such heat pump type air conditioning systems have been recently mountedon a part of high quality cars and so-called one box-type cars having arelatively large space, in which they a so-called dual air conditioningtype including a front unit for air-conditioning a front region (forexample, a front seat part) of the passenger compartment and a rear unitfor air-conditioning a rear region (for example, a rear seat part) ofthe passenger compartment. Accordingly, the front and rear regions ofthe passenger compartment can be independently air-conditioned so as toachieve a comfortable air conditioning for the passenger compartment.Such air conditioning systems operate as follows: During the heatingoperation of the air conditioning system, the front unit uses enginecoolant as a heat source while the rear unit uses as a heat source ahigh temperature and pressure refrigerant which is compressed by thecompressor. Such air conditioning systems are arranged to pump up heatfrom the low temperature outside air in the circulating process orrefrigeration cycle of the refrigerant and uses it to heat the passengercompartment.

Such air conditioning systems encounter with problems in case ofcarrying out the heating operation of the passenger compartment of theautomotive vehicle. For example, when the temperature of the outside airis low, for example, in the morning in winter, the temperature of theengine coolant is low at the engine starting, and the temperature riseof the refrigerant is not sharp. Consequently, it is difficult to putthe air conditioning system into such a state as to blow warm air intothe passenger compartment simultaneously with the starting of operationof the air conditioning system, so that the air conditioning system islow in quick or instant heating ability and is low in heatingperformance. Particularly in the one-box type cars which provided with adiesel engine and are large in space of the passenger compartment, therate of temperature rise of the engine coolant is low as compared withautomotive vehicles provided with a usual gasoline engine while it isrequired to heat the large space, and therefore there is such a tendencyas to be low in quick heating ability and heating performance for thepassenger compartment. In view of this, a heat pump type airconditioning system of the following type has now been proposed: Therefrigerant is heated under the action of heat of the coolant for adriving system in an electric vehicle thereby to be increased inenthalpy and becoming high in temperature. Accordingly, the thus heatedrefrigerant exhibits a high heating ability of the air conditioningsystem. Such a heat pump type air conditioning system is disclosed inJapanese Patent Provisional Publication No. 7-101227.

Thus, the various heat pump type air conditioning systems andimprovements therefor have been developed and proposed.

However, the above-discussed heat pump type air conditioning systemshave encountered a variety of drawbacks which will be discussed below.That is, it is usual to carry out an on-off control of the compressor bymaking an on-off control of a magnetic clutch (disposed between thecompressor and an engine) in accordance with the discharge pressure ofthe compressor in order to protect the compressor from its breakage whenthe discharge pressure of the compressor excessively rises. Thedischarge pressure of the compressor is detected by a pressure sensor.However, in case of protecting the compressor only under the on-offcontrol of the compressor, shock (impact) and noise are generated withthe on-off control (for example, the on-off action of the magneticclutch) of the compressor. It will be understood that the on-off actionsof the magnetic clutch correspond respectively to a connection and adisconnection between the compressor and the engine. These connectionand disconnection tend to readily be transmitted as shock to the driver,thereby lowering the drivability of the vehicle.

Further, in order to cause the heat pump type air conditioning systemsto exhibit a high heating performance, it is required to recover therefrigerant accumulated in the exterior heat exchanger to the compressorthereby using a large amount of the refrigerant for the heatingoperation of the air conditioning system. In this regard, theabove-discussed air conditioning systems of the dual air conditioningtype mounted on the one box-type cars and the like have a relativelylarge volume condenser and a relatively long piping, so that aconsiderable time is required to recover the refrigerant. Additionally,for example in case of accomplishing the refrigeration and heatingoperations of only the rear unit, the refrigerant becomes unnecessaryfor the front unit. Accordingly, if the refrigerant (for the front unit)accumulated in the evaporator and the like are recovered, a large amountof the liquid state refrigerant is supplied to the compressor, therebycausing the fears of compressing the liquid state refrigerant, and ofcleaning the inside of the compressor with the liquid state refrigerant.This degrades the reliability of the compressor itself.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved heatpump type air conditioning system for an automotive vehicle, by whichdrawbacks encountered in conventional heat pump type air conditioningsystems can be effectively overcome.

Another object of the present invention is to provide an improved heatpump type air conditioning system for an automotive vehicle, whicheffectively improves drivability of the vehicle while being effectivelyprotected from being damaged, and additionally high in reliability andlow in production cost.

A further object of the present invention is to provide an improved heatpump type air conditioning system for an automotive vehicle, which ishigh in reliability for a compressor itself and for recovery of arefrigerant.

A still further object of the present invention is to provide animproved heat pump type air conditioning system for an automotivevehicle, which includes a refrigerant recovery system by which a largeamount of refrigerant can be effectively recovered for a short time,thereby ensuring a high heating performance of the air conditioningsystem.

An aspect of the present invention resides in a heat pump type airconditioning system (A) for an automotive vehicle. The heat type airconditioning system comprises a first unit (10) including a heater core(11) through which an engine coolant of an engine flows, and a firstheat exchanger (12) which forms part of a refrigeration cycle includinga compressor (1) and a first condenser (3), a refrigerant circulating inthe refrigeration cycle. A second unit (20) is provided including asecond condenser (21) and a second heat exchanger (22) which are fluidlyconnected in parallel with the first heat exchanger (12). A valve (V2)is fluidly connected in series with the second condenser (21) anddisposed such that a part of the refrigerant is introduced through thevalve into the second condenser (21) and said second heat exchanger(22). A sub-heat exchanger (30) is disposed outside the first and secondunits and fluidly connected in series with the second heat exchanger(22), the refrigerant flowing from the second heat exchanger (22) beingintroduced into the sub-heat exchanger to be heated by a part of theengine coolant, the refrigerant discharged from the sub-heat exchangerbeing returned to the compressor. An electromagnetic clutch (40) isprovided such that the compressor (1) is drivably connectable with theengine therethrough, the electromagnetic clutch being engaged toestablish a driving connection between the compressor so as to operatethe compressor and disengaged to cut the driving connection so as tomake the compressor inoperative. A control device (C) is operativelyconnected to the electromagnetic clutch (40) for controlling theelectromagnetic clutch to be disengageable in accordance with atemperature within the air conditioning system (A).

According to this aspect, by virtue of the fact that the electromagneticclutch is controlled to be disengageable in accordance with thetemperature within said air conditioning system, the time cycle of theon-off (engaging and disengaging) actions of the electromagnetic clutchis prolonged thereby reducing the frequency of changeover from theconnecting state (between the engine and the compressor) to thedisconnecting state (between the engine and the compressor) and viceversa. This improves the drivability of the automotive vehicle on whichthe air conditioning system is mounted. Additionally, the reducedfrequency of the changeover minimizes a pressure variation in the airconditioning system while contributing to protecting the airconditioning system itself.

Another aspect of the present invention resides in a heat pump type airconditioning system for an automotive vehicle. The heat pump type airconditioning system comprises a first unit (110) including a heater core(111) through which an engine coolant of an engine flows, and a firstevaporator (112) which forms part of a first refrigeration cycleincluding a first condenser (103), a first liquid tank (104 a) and afirst expansion valve (105 a) which are fluidly connected in series witheach other, the first refrigeration cycle being supplied with arefrigerant discharged from a compressor (101) driven by the enginethrough a first valve (V11), the compressor being fluidly connected inseries with the first evaporator (112). A second unit (120) includes asecond condenser (121) and a second evaporator (122) which is fluidlyconnected in series with the second condenser (121) through a secondliquid tank (104 b) and a second expansion valve (105 b), the secondcondenser (121), and the second evaporator (122) being fluidly connectedin series with the compressor (101) and forming part of a secondrefrigeration cycle which is supplied with a part of the refrigerantdischarged from the compressor (101) through a second valve (V12). Arefrigerant recovery line (R1) is fluidly connected in series with thefirst condenser (103) to introduce the refrigerant discharged from thefirst condenser (103) into the second refrigeration cycle during aheating operation of the air conditioning system (A).

According to this aspect, by virtue of the refrigerant recovery line forintroducing the refrigerant discharged from the first condenser to thesecond refrigeration cycle during the heating operation of the airconditioning system, the refrigerant to be recovered is returned to thecompressor through the second refrigeration cycle, so that therefrigerant is put into its evaporated state and therefore there are nofear of compressing a liquid in the compressor, of arising flowing-outof oil, and of causing rinsing action with the refrigerant. As a result,the compressor 1 can normally operate without lowing the reliabilitythereof.

A further aspect of the present invention resides in a heat pump typeair conditioning system for an automotive vehicle. The heat pump typeair conditioning system comprises a compressor (206), an exteriorcondenser (207) disposed outside a passenger compartment of the vehicle,an interior condenser (205) disposed inside the passenger compartment, apressure-reducing device (209), and an interior evaporator disposedinside the passenger compartment which are connected in series with eachother through a refrigerant piping (212). A bypass passage (213) isformed bypassing the exterior condenser to allow the refrigerantdischarged from the compressor (206) to be introduced to the interiorcondenser (205) bypassing the exterior condenser (207). A flow passagechange-over device (220) is provided to introduce the refrigerantdischarged from the compressor (206) to the exterior condenser (207)during a refrigeration operation of the air conditioning system and tothe bypass passage (213) during a heating operation of the airconditioning system. A refrigerant recovery passage (230) is providedsuch that the refrigerant stayed in the exterior condenser (207) isreturned therethrough to a suction side of the compressor (206), therefrigerant recovery passage (230) being located to connect the outletside of the exterior condenser (207) and the suction side of thecompressor (206). A valve (231) is disposed in the refrigerant recoverypassage (230) to be opened to allow the refrigerant to flow through therefrigerant recovery passage and to be closed to prevent the refrigerantfrom flowing through the refrigerant recovery passage.

According to this aspect, the refrigerant can be recovered in its liquidstate from the outlet of the exterior condenser during the heatingoperation of the air conditioning system. Accordingly, a large amount ofthe refrigerant can be recovered for a short time without causing areverse flow of the refrigerant to the exterior condenser. The amount ofthe refrigerant within the heating cycle can be always maintained at asuitable level during the heating operation of the air conditioningsystem. This solves the problems of lowering the heating performance dueto the heating operation under a refrigerant-shortage condition and oflowering a lubricating ability, thereby improving the performance andreliability of the air conditioning system.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, same reference numerals (characters) designate sameelements and parts throughout all figures, in which:

FIG. 1 is a diagrammatic view of a first embodiment of a heat pump typeair conditioning system according to the present invention;

FIG. 2 is a graph showing relative relationships between the temperatureof intake air in a rear unit and the discharge pressure of a compressorin the air conditioning system of FIG. 1;

FIG. 3 is a diagrammatic view of a modified example of the firstembodiment heat pump type air conditioning system of FIG. 1;

FIG. 4 is a diagrammatic view of a second embodiment of the heat pumptype air conditioning system according to the present invention;

FIG. 5 is a diagrammatic view of a third embodiment of the heat pumptype air conditioning system according to the present invention;

FIG. 6 is a diagrammatic view of a modified example of the thirdembodiment heat pump type air conditioning system of FIG. 4;

FIG. 7 is a diagrammatic view of another modified example of the thirdembodiment heat pump type air conditioning system of FIG. 5; and

FIG. 8 is a diagrammatic view of a further modified example of the thirdembodiment heat pump type air conditioning system of FIG. 5; and

FIG. 9 is a schematic illustration of a main condenser forming part ofthe heat pump type air conditioning system of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1 to 3, a first embodiment of a heat pump typeair conditioning system for an automotive vehicle is illustrated by thereference character A. The air conditioning system A of this embodimentcomprises front or first unit 10 and a rear or second unit 20. The frontunit 10 is arranged to condition air which is selectively drawn from theinside and the outside of a passenger compartment (not shown) of theautomotive vehicle under the action of a fan (not shown) and to blow theconditioned air toward a front seat for vehicle passenger. The rear unit20 is arranged to condition air which is selectively drawn from theinside and outside of the passenger compartment under the action of afan and to blow out the conditioned air toward a rear seat for vehiclepassenger. Accordingly, this air conditioning system A is called a dualair conditioning system.

The front unit 10 includes a casing 10 a defining thereinside an airflow passage 10 f in which air flows in a direction (air flow direction)indicated by an arrow F1. A heater core 11 and a first heat exchanger 12are disposed in the air flow passage 10 f and located respectively atthe downstream and upstream sides relative to the air flow direction F1.The heater core 11 is arranged such that engine coolant (hot water)heated by an engine 2 is circulated therethrough. More specifically, thefront unit 10 includes an intake unit (not identified), a cooling unit(not identified) and a heater unit (not identified) which are disposedin the order mentioned in the air flow direction in the casing 10 athough not clearly shown. The intake unit includes an intake door (notshown) and the above-mentioned fan. The cooling unit includes the firstheat exchanger 12. The heat unit includes an air mixing door (not shown)and the heater core 11. The air mixing door is disposed in front of theheater core 11 and arranged to control the ratio in flow amount betweenhot air passing through the heater core 11 and cool air bypassing theheater core 11 thereby to prepare air having a predetermined temperaturein a region downstream of the heater core 11, and arranged to preventair from passing through the heater core 11 Additionally, a variety ofvents (air blow openings) are formed at the downstream side of theheater core 11 of the heater unit so as to blow the air (having beencontrolled in temperature) prepared upon mixing the hot air and the coolair toward the front seat inside the passenger compartment, though notshown.

The rear unit 20 includes a casing 20 a defining thereinside an air flowpassage 20 f in which air flows in a direction (air flow direction)indicated by an arrows F2. A second condenser 21 and a second heatexchanger 22 are disposed in the air flow passage 20 f and locatedrespectively at the downstream and upstream sides relative to the airflow direction F2. More specifically, the rear unit 20 includes anintake unit (not identified), a cooling unit (not identified) and aheater unit (not identified) which are disposed in the order mentionedin the air flow direction in the air flow passage 21 similarly to thefront unit 10, though not clearly shown. The intake unit includes anintake door (not shown) and the above-mentioned fan. The cooling unitincludes the second heat exchanger 22. The heater unit includes an airmixing door (not shown) and the second condenser 21. The air mixing dooris disposed in front of the second condenser 21 and arranged to controla ratio in flow amount between hot air passing through the secondcondenser 21 and cool air bypassing the second condenser 21 thereby toprepare air having a predetermined temperature in a region downstream ofthe second condenser 21, and arranged to prevent air from passingthrough the second condenser 21. Additionally, a variety of vents (airblow openings) are formed at the downstream side of the second condenser21 of the heater unit so as to blow air (having been controlled intemperature) prepared upon mixing the hot air and the cool toward therear seat inside the passenger compartment, though not shown.

In this embodiment, the air conditioning system A includes a firstrefrigeration cycle or circuit and a second refrigeration cycle orcircuit. The first refrigeration cycle is constituted of a compressor21, a first condenser 3, a liquid tank 4 a, a first valve V1, a firstexpansion valve 5 a, and the first heat exchanger 12 (in the front unit10) which are connected to each other through a piping or lines for arefrigerant. The second refrigeration cycle is constituted of a secondvalve V2, the second condenser 21 (in the rear unit 20), a liquid tank 4b, a second expansion valve 5 b, the second heat exchanger 22 (in therear unit 20), and a sub-heat exchanger 30 which are fluidly connectedto each other through a piping or lines for the refrigerant and inparallel with the first heat exchanger 12. A changeover in flow of therefrigerant between the first and second refrigeration cycles is carriedout under combination of the opening and closing actions of the firstvalve V1 and the second valve V2.

In order to realize a refrigeration operation and a heating operation ofthe air conditioning system A in the same cycle, a bypass circuit orpassage 3B is provided to allow the refrigerant discharged from thecompressor 1 to bypass the first condenser 3. A four-way valve 7 isprovided to cause flow of the refrigerant discharged from the compressor1 to be changed over from the first condenser 3 to the bypass circuit 3Band vice versa. In other words, under the action of the four-way valve7, the refrigerant from the compressor 1 is introduced to the bypasscircuit 3B during a heating operation of the air conditioning system Awhile to the first condenser 3 during a refrigeration operation of theair conditioning system A.

The four-way valve 7 includes a hermetically sealed casing which isformed with one inlet port Pi and three outlet ports Po. A slidingmember S is sidably disposed in the casing and arranged to establishcommunication between selected two of the three outlet ports Po, so thatone outlet port Po other than the selected two outlet ports Po isbrought into communication with the inlet port Pi. The inlet port Pi ofthe four-way valve 7 is in communication with the discharge side of thecompressor 1, while the three outlet ports Po of the four-way valve 7are respectively in communication with the inlet of the first condenser3, the suction side of the compressor 1 (through a refrigerant returncircuit or passage R), and the outlet of the first condenser 3 (throughthe bypass circuit 3B).

The four-way valve 7 is used for effecting the return circuit R. Thisreturn circuit R functions to once return a large amount of therefrigerant staying in the first condenser 3 and the like to thecompressor 1 in case that the engine coolant cannot be immediately usedas a heat source for heating the passenger compartment because thetemperature of outside air is low at starting of the heating operationof the air conditioning system A. This enables a large amount of therefrigerant to be used to attain a high performance heating.

Regarding the front unit 10, during the heating operation of the airconditioning system A, the refrigerant discharged from the compressor 1flows through the four-way valve 7, the bypass circuit 3B for the firstcondenser 3, the liquid tank 4 a, the first valve V1, the expansionvalve 5 a, and the first heat exchanger 12 in the order mentioned andthen returns to the compressor 1. During the refrigeration operation ofthe air conditioning system A, the refrigerant discharged from thecompressor 1 flows through the four-way valve 7, the first condenser 3,the liquid tank 4 a, the first valve V1, the expansion valve 5 a, andthe first heat exchanger 12 in the order mentioned and then returns tothe compressor 1.

The heater core 11 is arranged to be supplied with an engine coolantflown from the engine 2 by opening a hot water cock or valve 11 a in ahot water circuit or passage W.

Regarding the rear unit 20, both during the refrigeration and heatingoperations of the air conditioning system A, the refrigerant dischargedfrom the liquid tank 4 a flows through the second valve V2, the secondcondenser 21, the liquid tank 4 b, the second expansion valve 5 b, thesecond heat exchanger 22, and the sub-heat exchanger 30 in the ordermentioned and returns to the compressor 1.

The sub-heat exchanger 30 is disposed outside the air flow passages 10f, 20 f of the front and rear units 10, 20. The engine coolant from theengine 2 is introduced into the sub-heat exchanger 30 by opening a hotwater cock or valve 11 b in the hot water circuit W, in which a heatexchange is made between the engine coolant and the refrigerant flowingthrough the sub-heat exchanger 30. In other words, the refrigerantflowing through the sub-heat exchanger 30 is heated by the enginecoolant, so that the refrigerant makes its isoentropic change. Therefrigerant having make its isoentropic change is returned to thecompressor 1 thereby causing the air conditioning system A to exhibit ahigher heating performance.

The compressor 1 is drivably connected to the engine 2 through anelectromagnetic clutch 40. The electromagnetic clutch 40 makes itson-off actions under its on-off control. More specifically, theelectromagnetic clutch 40 is switched ON to be engaged thereby totransmit a rotational power from the engine 2 to the compressor 1, whileswitched OFF to be disengaged thereby to prevent the rotational powerfrom the engine 2 from being transmitted to the compressor 1. The on-offcontrol of the electromagnetic clutch 40 is made in accordance with atemperature (intake air temperature) of air taken into the air flowpassage 20 f of the rear unit 20. More specifically, a temperaturesensor SE1 is disposed in the air flow passage 20 f in the intake unitof the rear unit 20 in order to detect the intake air temperature. Asignal (representative of the intake air temperature) is transmittedfrom temperature sensor SE1 to a control unit C. The control unit Cmakes the on-off control of the electromagnetic clutch 40 in accordancewith the signal from temperature sensor SE1. In other words, when thetemperature sensor SE1 detects that the intake air temperature in therear unit 20 is not lower than a predetermined level (for example, 30°C.), the control unit C controls the electromagnetic valve 40 to beswitched OFF to be disengaged. When the electromagnetic valve 40 isdisengaged, the compressor 1 is switched OFF to stop its compressionaction. When the electromagnetic valve 40 is engaged upon being switchedON, the compressor is switched ON to make its compression action. Thus,an on-off control of the compressor 1 is accomplished in accordance withthe intake air temperature in the rear unit 20.

According to experiments, as shown in FIG. 2, it has been revealed thata proportional relationship exists between the intake air temperature (°C.) in the rear unit 2 and the discharge pressure (kg/cm²) of thecompressor though such a relationship is slightly changed according toengine speed (the revolution speed) of the engine 2. In FIG. 2, threerelationships respectively obtained at engine speeds of 800 rpm, 1500rpm and 3000 rpm are shown. A “Compressor-Off Region” indicated in FIG.2 represents a region where the compressor 1 is switched OFF to stop thecompression action of the compressor 1. This means that the same effectcan be obtained by accomplishing the on-off control of the compressor 1in accordance with the discharge pressure of the compressor 1 and inaccordance with the intake air temperature in the rear unit 20.

Here, in case that the on-off control of the compressor 1 isaccomplished in accordance with the intake air temperature in the rearunit 20, a response in control is lower than that in case that theon-off control of the compressor 1 is accomplished in accordance withthe discharge pressure of the compressor 1. However, a time cycle of theon-off (engaging and disengaging) actions of the electromagnetic clutch40 is prolonged thereby reducing a frequency of changeover from aconnecting state (between the engine 2 and the compressor 1) to adisconnecting state (between the engine 2 and the compressor 1) and viceversa. This improves a drivability of the automotive vehicle on whichthe air conditioning system A is mounted. Additionally, the reducedfrequency of the changeover reduces a pressure variation in the airconditioning system A and therefore is desirable from the view point ofprotecting air conditioning system A itself.

Therefore, in this embodiment, operation of the air compressor 1 isstopped to stop the heating operation in the rear unit 20 when theintake air temperature in the rear unit 20 reaches the predeterminedlevel.

Next, manner of operation of the thus arranged first embodiment heatpump type air conditioning system A will be discussed hereinafter.

Initial Stage of Heating Operation

When the temperature of the outside air (air outside the vehicle) is low(for example, about −10° C. to about +5° C.) so that the engine coolanthas a lower temperature at the starting of the heating operation of theair conditioning system A, it is difficult to use the engine coolant forheating the passenger compartment, employing the heater core 11. At sucha time, the refrigerant has been staying inside the first condenser 3and the like, and therefore a large amount of the refrigerant does notexist in the compressor 1. In case of accomplishing heating for thefront and rear seats under this condition, a setting is made as follows:The first and second valves V1, V2 are opened; and the four-way valve 7is in the state shown in FIG. 1.

When the compressor 1 is switched ON to be operated under thiscondition, the refrigerant which has been staying mainly in the firstcondenser 3 and the like is introduced into the suction side of thecompressor 1 through the four-way valve 7 and the refrigerant returncircuit R so as to be recovered. As a result, a large amount of therefrigerant is discharged from the compressor 1. The high temperatureand pressure refrigerant discharged from the compressor 1 flows throughthe four-way valve 7, the bypass circuit 3B, the liquid tank 4 a, thefirst valve V1, the expansion valve 5 a and the first heat exchanger 12in the order mentioned.

Under starting of the engine 1, the engine coolant whose temperaturehaving been raised to some extent flows into the heater core 11;however, the engine coolant at this time is not sufficiently raised intemperature, and therefore it is not desirable to use the engine coolantto heat the passenger compartment. Accordingly, in such a condition, itis preferable that the hot water cock 11 a is closed to prevent theengine coolant from flowing into the heater core 11 or that air in theair flow passage 10 f cannot flow through the heater core 11 under theaction of the intake door, in which the hot water cock 11 b is opened soas to allow the engine coolant to flow through the sub-heat exchanger30. By this, air introduced from the intake unit into the inside of thefront unit 10 is brought into contact with the first heat exchanger 12in which the high temperature and pressure refrigerant flows, in whichheat exchange is made between the air and the refrigerant. Thereafter,the air flows to the downstream side of the air flow passage 10 f andblown through the vents to the passenger compartment.

Concerning the rear unit 20, the flow of the high temperature andpressure refrigerant which is bifurcated after flowing out of the liquidtank 4 a enters the second condenser 21 through the second valve V2.Here, heat exchange is made between the refrigerant and the air flowingthrough the air flow passage 20 f of the rear unit 20, so that the airto be supplied to the passenger compartment is heated. Thereafter, therefrigerant is condensed and to become medium in temperature and high inpressure, and is subjected to an adiabatic expansion in the secondexpansion valve 5 b, so that the refrigerant becomes further low intemperature and low in pressure. Then, the refrigerant flows into thesecond heat exchanger 22 which functions as an evaporator. Here, heatexchange is made between the refrigerant and the air flowing through theair flow passage 20 f of the rear unit 20, in which the refrigerantevaporates after cooling air and then becomes low in temperature and inpressure to flow into the sub-heat exchanger 30. Accordingly, the air tobe supplied to the passenger compartment is first dehumidified andrefrigerated by the second heat exchanger 22, and therefore heated bythe second condenser 21.

It is preferable that a door (not shown) is disposed in front of thesecond heat exchanger 22 to prevent the air from passing through thesecond heat exchanger 22 during the heating operation of the airconditioning system A since it is not desirable that the air is cooledby the second heat exchanger 22 during the heating operation.

The low temperature and pressure refrigerant flowing through thesub-heat exchanger 30 takes in the heat of the engine coolant and risesin temperature to make its isotropic change. The refrigerant having madeits isotropic change is returned to the compressor 1 to be againcompressed, so that the temperature of the refrigerant discharged fromthe compressor 1 rises. In this case, the refrigerant to be returned tothe compressor 1 is heated in the second heat exchanger 22 by the airand additionally heated in the sub-heat exchanger 30 by the enginecoolant, so that a so-called two-stage heating is made to therefrigerant. This causes the air conditioning system A to exhibit a highheating performance while improving an instant or quick heatingcharacteristics for the passenger compartment. Besides, when the thusheated refrigerant is again compressed by the compressor 1, atemperature rise of the refrigerant is further promoted. When the thusheated refrigerant circulates to again reach the first and second heatexchangers 12, 22, the refrigerant is again heated here to obtain afurther high temperature thereby causing the air conditioning system Ato exhibit a further high heating performance so that high temperatureair is blown into the passenger compartment. This tendency is amplifiedwith a time lapse, thus greatly improving the instant or quick heatingcharacteristics of the air conditioning system A.

When the temperature of the engine coolant has risen in the course ofthe above operation of the air conditioning system A, the heatingability of the sub-heat exchanger 30 is increased while the heatingability of the heater core 11 is increased in connection with the frontunit 10, so that considerable high temperature air is blown into thepassenger compartment under the combination effect of the increasedheating abilities of the sub-heat exchanger and the heater core 11.

Concerning the rear unit 20, the heating ability of the second condenser21 is increased, and therefore considerably high temperature air isblown into the passenger compartment. It will be understood that thedoor which has been closed in front of the second heat exchanger 22 isallowed to be opened when the heating ability of the second condenser 21is increased as discussed above, thereby making it possible toaccomplish a so-called dehumidifying heating in which dehumidified airis heated. This defogs a window glass near the rear seat, therebysecuring a safety driving of the vehicle.

During Stable Heating Operation

When the temperature of the engine coolant rises to some extent so thatthe temperature within the passenger compartment rises to some extent,the hot water cock 11 b is closed thereby preventing the engine coolantfrom flowing into the sub-heat exchanger 30. This prevents therefrigerant from being unnecessarily heated thereby to accomplish anormal heating operation of the air conditioning system A.

In this embodiment, when the intake air temperature within the rear unit20 becomes a level not lower than the predetermined temperature, thetemperature sensor SE1 detects the temperature level and provides thesignal representative of the temperature level to the control unit C.The control unit C causes the electromagnetic clutch 40 to be switchedOFF or disengaged, thereby stopping the compression action of thecompressor 1. In contrast, when the intake air temperature within therear unit 20 lowers to a level lower than the predetermined level, thecompression action of the compressor 1 is again made. Thus, the on-offcontrol of the compressor 1 is accomplished in accordance with thetemperature of the air flowing through the air flow passage 20 f in therear unit 20. Since the on-off control of the compressor 1 isaccomplished in accordance with the intake air temperature in the rearunit 20, a response in control may be lower than that in case that theon-off control of the compressor 1 is accomplished in accordance withthe discharge pressure of the compressor 1. However, the time cycle ofthe on-off (engaging and disengaging) actions of the electromagneticclutch 40 is prolonged thereby reducing the frequency of changeover fromthe connecting state (between the engine 2 and the compressor 1) to thedisconnecting state (between the engine 2 and the compressor 1) and viceversa. This improves a drivability of the automotive vehicle on whichthe air conditioning system A is mounted. Additionally, the reducedfrequency of the changeover minimizes a pressure variation in the airconditioning system A while contributing to protecting the airconditioning system A itself.

During Refrigeration Operation

In order to accomplish refrigeration for both the front and rear seats,the first and second valves V1, V2 are opened, and the sliding member Sof the four-way valve 7 is moved. Under this state, when the compressor1 is operated to make its compression action, the refrigerant dischargedfrom the compressor 1 flows through the four-way valve 7, the firstcondenser 3, the liquid tank 4 a, the first valve V1, the firstexpansion valve 5 a, and the first heat exchanger 12 in the ordermentioned, in the first refrigeration cycle. The flow of the refrigerantis bifurcated at the downstream side of the liquid tank 4 a, so that therefrigerant flows through the second valve V2, the second condenser 21,the second expansion valve 5 b, the second heat exchanger 22, and thesub-heat exchanger 30 in the order mentioned.

By this, the air introduced into the air flow passage 10 f in the frontunit 10 is subjected to heat exchange at the first heat exchanger 12which functions as an evaporator, in which the heat exchange is madebetween the air and the low temperature and pressure refrigerant flowingthrough the heat exchanger 12 thereby to provide dehumidified lowtemperature air. This air is distributed to the side of the heater core11 and the side of a bypass passage (not shown) bypassing the heatercore 11 under the action of the air mixing door, thereby preparing coolair and hot air. The cool air and the hot air are mixed or not mixed toobtain air having a predetermined temperature. The air having thepredetermined temperature is blown through the vents into the passengercompartment.

Concerning the rear unit 20, the refrigerant which has been lowered inpressure by the second expansion valve 5 b flows into the second heatexchanger 22. The air refrigerated by the second heat exchanger 22 isdistributed to the side of the second condenser 21 and to the side of abypass passage (not shown) bypassing the second condenser 21 under theaction of the air mixing door, thereby preparing cool air and hot air.The cool air and the hot air are mixed or not mixed to prepare airhaving a predetermined temperature. The air having the predeterminedtemperature is blown through the vents into the passenger compartment.

The refrigerant discharged from the second heat exchanger 22 flows intothe sub-heat exchanger 30; however, the refrigerant is returned at thisstate to the compressor 1 since the hot water cock 11 b is closed toprevent the engine coolant from flowing into the sub-heat exchanger 30.

In order to accomplish refrigeration only for the front seat, the secondvalve V2 is closed In order to accomplish refrigeration only for therear seat, the first valve V1 is closed.

While only an example of the first embodiment has been shown anddescribed, variations thereto will occur to those skilled in the artwithin the scope of the present inventive concepts which are delineatedby the claims. For example, while the four-way valve 7 and therefrigerant return circuit R have been shown and described as beingprovided to return the refrigerant staying in the refrigerant circuit tothe compressor 1, it will be understood that the air conditioning systemA may be operated without returning the staying refrigerant to thecompressor 1, in which the four-way valve 7 is replaced withopen-and-close valves V3, V4 which are respectively disposed in theinlet of the first condenser 3 and the bypass circuit 3B as shown inFIG. 3.

According to the first embodiment air conditioning system A, by virtueof the fact that the electromagnetic clutch is controlled to bedisengageable in accordance with the temperature within said airconditioning system, the time cycle of the on-off (engaging anddisengaging) actions of the electromagnetic clutch is prolonged therebyreducing the frequency of changeover from the connecting state (betweenthe engine and the compressor) to the disconnecting state (between theengine and the compressor) and vice versa. This improves the drivabiltyof the automotive vehicle on which the air conditioning system ismounted. Additionally, the reduced frequency of the changeover minimizesa pressure variation in the air conditioning system while contributingto protecting the air conditioning system itself.

FIG. 4 illustrates a second embodiment of the heat pump type airconditioning system A for an automotive vehicle, similar to the firstembodiment air conditioning system. The air conditioning system A ofthis embodiment comprises front or first unit 110 and a rear or secondunit 120. The front unit 110 is arranged to condition air which isselectively drawn from the inside and the outside of a passengercompartment (not shown) of the automotive vehicle under the action of afan (not shown) and to blow the conditioned air toward a front seat forvehicle passenger. The rear unit 120 is arranged to condition air whichis selectively drawn from the inside and outside of the passengercompartment under the action of a fan and to blow out the conditionedair toward a rear seat for vehicle passenger. Accordingly, this airconditioning system A is called a dual air conditioning system.

The front unit 110 includes a casing 110 a defining thereinside an airflow passage 110 f in which air flows in a direction (air flowdirection) indicated by arrows F1. A heater core 111 and a first heatexchanger 112 are disposed in the air flow passage 111 f and locatedrespectively at the downstream and upstream sides relative to the airflow direction F. The heater core 111 is arranged such that enginecoolant (hot water) heated by an engine 102 is circulated therethrough.More specifically, the front unit 110 includes an intake unit (notidentified), a cooling unit (not identified) and a heater unit (notidentified) which are disposed in the order mentioned in the air flowdirection in the casing 110 a though not clearly shown. The intake unitincludes an intake door (not shown) and the above-mentioned fan. Thecooling unit includes the first heat exchanger 112. The heat unitincludes an air mixing door (not shown) and the heater core 111. The airmixing door is disposed in front of the heater core 112 and arranged tocontrol the ratio in flow amount between hot air passing through theheater core 111 and cool air bypassing the heater core 111 thereby toprepare air having a predetermined temperature in a region downstream ofthe heater core 111, and arranged to prevent air from passing throughthe heater core 111. Additionally, a variety of vents (air blowopenings) are formed at the downstream side of the heater core 111 ofthe heater unit so as to blow the air (having been controlled intemperature) prepared upon mixing the hot air and the cool air towardthe front seat inside the passenger compartment, though not shown.

The rear unit 120 includes a casing 120 a defining thereinside an airflow passage 120 f in which air flows in a direction (air flowdirection) indicated by arrows F2. A second condenser 121 and a secondevaporator 122 are disposed in the air flow passage 120 f and locatedrespectively at the downstream and upstream sides relative to the airflow direction F2. More specifically, the rear unit 120 includes anintake unit (not identified), a cooling unit (not identified) and aheater unit (not identified) which are disposed in the order mentionedin the air flow direction in the air flow passage 120 f similarly to thefront unit 110, though not clearly shown. The intake unit includes anintake door (not shown) and the above-mentioned fan. The cooling unitincludes the second evaporator 122. The heater unit includes an airmixing door (not shown) and the second condenser 121. The air mixingdoor is disposed in front of the second condenser 121 and arranged tocontrol a ratio in flow amount between hot air passing through thesub-condenser and cool air bypassing the second condenser 121 thereby toprepare air having a predetermined temperature in a region downstream ofthe second condenser 121, and arranged to prevent air from passingthrough the second condenser 121. Additionally, a variety of vents (airblow openings) are formed at the downstream side of the second condenser121 of the heater unit so as to blow air (having been controlled intemperature) prepared upon mixing the hot air and the cool toward therear seat inside the passenger compartment, though not shown.

In this embodiment, the air conditioning system A includes a firstrefrigeration cycle or circuit (not identified) and a secondrefrigeration cycle or circuit (not identified). The first refrigerationcycle includes a compressor 101, a first valve V11, a first condenser103, a first liquid tank 104 a, a first expansion valve 105 a, and thefirst evaporator 112 which are connected in series with each other inthe order mentioned through a piping or lines for refrigerant. Thesecond refrigeration cycle includes a second valve V12, the secondcondenser 121, a second liquid tank 104 b, a second expansion valve 105b, the second evaporator 122, and a sub-heat exchanger 130 which areconnected in series with each other in the order mentioned through apiping or lines for the refrigerant. A changeover operation in flow ofthe refrigerant between the first and second refrigeration cycles iscarried out under the combination of the opening and closing actions ofthe first valve V11 and the second valve V12. Additionally, arefrigeration operation and a heating operation of the air conditioningsystem A can be realized in the same cycle.

In this embodiment, a refrigerant recovery circuit or line R1 isprovided to introduce the refrigerant discharged from the firstcondenser 103 into the second refrigerant cycle. Specifically, therefrigerant recovery line R is arranged to return the refrigerantdischarged from the first condenser 103 into the second liquid tank 104b. More specifically, the refrigerant recovery line R1 includes a lineor passage P through which the outlet of the first condenser 103 and theoutlet of the second condenser 121 are fluidly connected with eachother. A third valve V13 and a one-way valve 140 are disposed in thepassage P. The third valve V13 is opened during the heating operation ofthe air conditioning system A. The one-way valve 140 is arranged todirect flow of the refrigerant from the first condenser 103 to thesecond evaporator 122. Accordingly, at the starting of the heatingoperation of the air conditioning system A, the refrigerant stayed inthe first condenser 103 is returned to the second refrigeration cyclethereby accomplishing a high performance heating operation of the airconditioning system A upon using a large amount of the refrigerant.

The heating operation can be accomplished with the front unit 110. Incase of the heating operation with the front unit 110, the refrigerantdischarged from the compressor 1 flows through the first valve V11, thefirst condenser 103, the first liquid tank 104 a, the first expansionvalve 5 a and the first evaporator 112 in the order mentioned and thenreturns to the compressor 1. This flow of the refrigerant is the same asthat during the refrigeration operation of the air conditioning systemA. During the normal heating operation of the air conditioning system A,a hot water cock or valve 111 a in a hot water circuit W is opened toallow engine coolant (relatively high in temperature) flowing out of theengine 102 to be introduced into the heater core 111. The heater core111 functions to heat the air which has been cooled by the firstevaporator 112. It will be understood that the engine coolant of theengine 102 circulates through the hot water circuit W.

During the refrigeration and heating operations of the air conditioningsystem A, concerning the rear unit 120, the refrigerant whose flow hasbeen bifurcated from the first refrigeration cycle upon opening of thesecond valve V12 flows through the second condenser 121, the secondliquid tank 104 b, the second expansion valve 105 b, the secondevaporator 122 and the sub-heat exchanger 130 in the order mentioned andthen returns to the compressor 101.

The sub-heat exchanger 130 is disposed outside the air flow passages 110f, 120 f of the front and rear units 110, 120. The engine coolant isintroduced from the engine 102 into the sub-heat exchanger 130 byopening the hot water cock 111 b, in which heat exchange is made betweenit and the refrigerant flowing through the sub-heat exchanger 130. Thatis, in this sub-heat exchanger 130, the refrigerant flowing through thesub-heat exchanger 130 is heated by the engine coolant thereby makingits isoentropic change. The engine coolant having made its isoentropicchange is returned to the compressor 101 thereby causing the airconditioning system A to exhibit a high heating performance.

During Refrigerant Recovering Operation (Initial Stage of HeatingOperation

When the temperature of the outside air (air outside the vehicle) is low(for example, about −10° C. to about +5° C.) so that the engine coolanthas a lower temperature at the starting of the heating operation of theair conditioning system A, it is difficult to use the engine coolant forheating the passenger compartment, employing the heater core 111. Atsuch a time, the refrigerant has stayed inside the first condenser 103and the like, and therefore a large amount of the refrigerant does notexist in the compressor 101. In case of accomplishing heating for thefront and rear seats under this condition, a setting is made, there isthe fear of occurring a shortage of the refrigerant. In view of this,first the first and third valves V11, V13 are opened, while the secondvalve V12 is closed.

When the compressor 101 is operated to make its compression action, apart of the refrigerant stayed in the first condenser 103 flows throughthe first condenser 103, the first liquid tank 104 a, the firstexpansion valve 105 a, and the first evaporator 112 (which form part ofthe first refrigeration cycle) in the order mentioned and then returnsto the compressor 101. That is, a part of the staying refrigerant isevaporated during passage through constituting elements or parts of thefirst regeneration cycle and recovered to the compressor 101, therebyrelatively minimizing the amount of the refrigerant in a liquid state.

The other part of the refrigerant stayed in the first condenser 103 isdrawn under the suction of the compressor 101 and flows through thethird valve V13, the relatively long passage P and the one-way valve 140(constituting the refrigerant recovering line R) in the order mentioned,and then is introduced to the second refrigeration cycle.

A part of the thus introduced refrigerant is stored in the second liquidtank 104 b for use in the next heating operation, while the other partof the refrigerant flows through the second expansion valve 105 b, thesecond evaporator 122, and the sub-heat exchanger 130 in the ordermentioned and flows into the compressor 101. Also in this case, therefrigerant is recovered after passing through the constituting elementsor parts of the second refrigeration cycle, and therefore the amount ofthe refrigerant in a liquid state is minimized. Additionally, even whensuch a large amount of the refrigerant is returned to the compressor,the refrigerant can be heated to some extent by the engine coolant,thereby further promoting evaporation of the refrigerant so as tominimize the amount of the liquid state refrigerant to be returned.

This establishes a condition in which a large amount of the refrigerantis discharged from the compressor 101 while a large amount of therefrigerant is recovered to the compressor 101. In this refrigerantrecovery, the amount of the liquid state refrigerant is relativelysmall, and therefore there are no fear of compressing a liquid in thecompressor 101, of arising flowing-out of oil, and of causing rinsingaction with the refrigerant. As a result, the compressor 101 cannormally operate thereby providing no fear of lowing the reliability ofthe compressor 101. Additionally, since the refrigerant recovering lineR is constituted of the third valve V13, the passage P and the one-wayvalve 140, the air conditioning system A is low in production cost andadvantageous from the economical view point.

During Heating Operation

In case of carrying out the heating operation, the first valve V11 andthe third valve V13 are closed thereby to prevent a backward flow of therefrigerant from the side of the second refrigeration cycle, while thesecond valve V12 is opened By this, a large amount of the hightemperature and pressure refrigerant discharged from the compressor 101flows through the second valve V12, the second condenser 121, the secondliquid tank 104 b, the second expansion valve 105 b, the secondevaporator 122 and the sub-heat exchanger 130 in the order mentioned.

Upon starting the engine 1, the engine coolant whose temperature hasbeen raised to some extent flows into the heater core 111 and thesub-heat exchanger 130; however, the engine coolant at this time is notsufficiently raised in temperature, and therefore it is not desirable touse the engine coolant for heating the passenger compartment.Accordingly, in such a condition, it is preferable for the front unit110 that the hot water cock 111 a is closed to prevent the enginecoolant from flowing into the heater core 111 or that air in the airflow passage 110 f cannot flow through the heater core 111 under theaction of the intake door. At this time, for the rear unit 120, the hotwater cock 111 b is opened so as to allow the engine coolant to flowthrough the sub-heat exchanger 130. By this, the heating operation isnot accomplished in the side of the front unit 110; however, in the sideof the rear unit 120, the heating operation is accomplished to heat theair inside the passenger compartment since the high temperature andpressure refrigerant flows through the second valve V12 to the secondcondenser 121 so that heat exchange is made between the refrigerant andthe air inside the passenger compartment.

The refrigerant becomes medium in temperature and high in pressure uponbeing condensed after heating the air inside the passenger compartment.Then, the refrigerant is subjected to an adiabatic expansion at thesecond expansion valve 105 b, and therefore becomes further low intemperature and low in pressure. This refrigerant flows into the secondevaporator 122, in which heat exchange is made between the refrigerantand the air inside the passenger compartment thereby refrigerating theair. However, it is not preferable that this refrigerated cool air isblown into the passenger compartment, and therefore the cool air is tobe discharged to the outside of the vehicle; or a door (not shown) maybe provided in front of the second evaporator 122 so as to prevent theair from passing through the second evaporator 122.

Then, the refrigerant which has been evaporated in the second evaporator122 to become low in temperature and pressure flows into the sub-heatexchanger 130, so that the refrigerant takes in heat of the enginecoolant in the sub-heat exchanger 130 and rises in temperature to makeits isoentropic change. This refrigerant is thereafter returned to thecompressor 101 and again compressed so that the refrigerant dischargedfrom the compressor 101 rises. In this case, the refrigerant to bereturned to the compressor 1 is heated by the air in the secondevaporator 122 and heated by the engine coolant in the sub-heatexchanger 130, so that a so-called two-stage heating is accomplished forthe refrigerant. Accordingly, the air conditioning system A can exhibita high heating performance while improving an instant or quick heatingcharacteristics of the air conditioning system A. Additionally, when therefrigerant upon being heated is again compressed by the compressor 101,a temperature rise of the refrigerant is further promoted. Then, whenthe refrigerant again reaches the second evaporator 122, the refrigerantis again heated and becomes further higher in temperature, thusproviding a further high heating performance of the air conditioningsystem A so that high temperature air is blown to the passengercompartment A. This tendency is amplified with a time lapse, thusgreatly improving the instant or quick heating characteristics of theair conditioning system A.

When the temperature of the engine coolant has risen in the course ofthe above operation of the air conditioning system A, the engine coolantis flown into the heater core 111 of the front unit 110 to accomplishthe heating operation also at the side of the front unit 110, so thatthe whole engine compartment is heated. Additionally, the heatingability of the sub-heat exchanger 130 is increased as the heatingability of the engine coolant is increased in connection with the frontunit 110, so that considerable high temperature air is blown into thepassenger compartment under the combination effect of the increasedheating abilities of the sub-heat exchanger and the engine coolant.

It will be understood that the door which has been closed in front ofthe second evaporator 122 is allowed to be opened when the heatingability of the second condenser 121 is increased, thereby making itpossible to accomplish a so-called dehumidifying heating in whichdehumidified air is heated. This defogs a window glass near the rearseat, thereby securing a safety driving of the vehicle.

During Stable Heating Operation

When the temperature of the engine coolant rises to some extent so thatthe temperature within the passenger compartment rises to some extent,the hot water cock 111 b of the sub-heat exchanger 130 is closed therebyto prevent the engine coolant from flowing into the sub-heat exchanger130. This prevents the refrigerant from being unnecessarily heated so asto accomplish a normal heating operation of the air conditioning systemA.

During Refrigeration Operation

The refrigeration operation can be accomplished for both the front andrear seats, or only for the front seat. In order to accomplish therefrigeration operation only for the front seat, the first valve V11 isopened, while the second valve V12 and the third valve V13 are closed.Under this condition, when the compressor 101 is operated to make itscompression action, the refrigerant discharged from the compressor 1flows through the first valve V11, the first condenser 103, the firstliquid tank 104 a, the first expansion valve 105 a and the firstevaporator 112 in the order mentioned for the first refrigeration cycle.By this, the air introduced through the intake unit into the air flowpassage 110 f of the front unit 110 is subjected to heat exchangebetween it and the low temperature and pressure refrigerant in the firstevaporator 112 thereby preparing dehumidified low temperature air. Thisair is distributed to the side of the heater core 111 and the side of abypass passage (not shown) bypassing the heater core 111 under theaction of the air mixing door, thereby preparing cool air and hot air.The cool air and the hot air are mixed or not mixed to obtain air havinga predetermined temperature. The air having the predeterminedtemperature is blown through the vents into the passenger compartment.

Concerning the rear unit 120, the second valve V12 is opened, so thatthe refrigerant which has been lowered in pressure by the secondexpansion valve 105 b flows also to the second evaporator 122. The airrefrigerated by the second evaporator 122 is distributed to the side ofthe second condenser 121 and to the side of a bypass passage (not shown)bypassing the second condenser 121 under the action of the air mixingdoor, thereby preparing cool air and hot air. The cool air and the hotair are mixed to prepare air having a predetermined temperature in adownstream region of the second condenser 121, or not mixed. Then, theair is blown through the vents into the passenger compartment.

In this case, the refrigerant discharged from the second evaporator 122flows into the sub-heat exchanger 130; however, the hot water cock 111 bis closed during the refrigeration operation thereby to prevent theengine coolant from flowing into the sub-heat exchanger 130. In order toaccomplish refrigeration only for the rear seat, the first valve V11 isclosed.

While only an example of the second embodiment has been shown anddescribed, variations thereto will occur to those skilled in the artwithin the scope of the present inventive concepts which are delineatedby the claims. For example, while the heat pump type air conditioningsystem A has been shown and described as including the sub-heatexchanger 130, the heat pump type air conditioning system may notnecessarily include the sub-heat exchanger 130. Additionally, whilerefrigerant recovering line R has been shown and described asestablishing communication between the outlet of the first condenser 103and the outlet of the second condenser 121, it will be appreciated thatthe refrigerant recovering line R may take other arrangements, in whichit is sufficient that the refrigerant recovering line R is arranged tointroduce the refrigerant in the first refrigeration cycle to the secondrefrigeration cycle.

According to the second embodiment air conditioning system A, by virtueof the refrigerant recovery line for introducing the refrigerantdischarged from the first condenser to the second refrigeration cycleduring the heating operation of the air conditioning system, therefrigerant to be recovered is returned to the compressor through thesecond refrigeration cycle, so that the refrigerant becomes itsevaporated state and therefore there are no fear of compressing a liquidin the compressor, of arising flowing-out of oil, and of causing rinsingaction with the refrigerant. As a result, the compressor 1 can normallyoperate without lowering the reliability thereof.

FIG. 5 illustrates a third embodiment of the air conditioning system Aaccording to the present invention, similar to the first embodiment airconditioning system. In this embodiment, the air conditioning system Acomprises an air conditioning unit 200 which is arranged to conditionair which is selectively drawn from the inside and the outside of apassenger compartment (not shown) of the automotive vehicle and to blowthe conditioned air toward a predetermined position in the passengercompartment.

The air conditioning unit 200 includes a duct 202 defining thereinsidean air flow passage (not identified) in which air flows in a direction(air flow direction) indicated by arrows F under the action of an blowerfan 203. An interior evaporator 204 and a sub-condenser 205 as aninterior condenser are disposed in the air flow passage and locatedrespectively at the upstream and downstream sides relative to the airflow direction F. The evaporator 204 functions to cool air flowingthrough the air flow passage upon evaporation of the refrigerant in theevaporator 204. The sub-condenser 205 functions to heat air flowingthrough the air flow passage upon condensation and liquefaction of thegasified refrigerant mainly during the heating operation of the airconditioning system A. More specifically, the air conditioning unit 200includes an intake unit (not identified), a cooling unit (notidentified) and a heater unit (not identified) which are disposed in theorder mentioned in the air flow direction in the air flow passage,though not clearly shown. The intake unit includes an intake door (notshown) and the above-mentioned blower fan 203. The cooling unit includesthe evaporator 204. The heater unit includes a rotatable air mixing door(not shown) and the sub-condenser 205. The air mixing door is disposedin front of the sub-condenser 205 and arranged to control a ratio inflow amount between hot air passing through the sub-condenser 205 andcool air bypassing the sub-condenser 205 thereby to prepare air having apredetermined temperature in a region downstream of the sub-condenser205, and arranged to prevent air from passing through the sub-condenser205. Additionally, a variety of vents (air blow openings) are formed atthe downstream side of the sub-condenser 205 of the heater unit so as toblow air (having been controlled in temperature) prepared upon mixingthe hot air and the cool toward the predetermined position inside thepassenger compartment, though not shown.

The air conditioning system A makes its cooling and heating operationsunder a cycle operation for the refrigerant thereby accomplishingcooling and heating (upon dehumidification) for the passengercompartment, under the action of a refrigeration cycle or circuit.

The air conditioning system A comprises a compressor 206 which isdisposed outside the air conditioning unit 200 and rotationally driventhrough a belt (not shown) by an engine (not shown). A main condenser207 as an exterior condenser is disposed outside the air conditioningunit 200 and adapted to function only during the heating operation ofthe air conditioning system A. The refrigeration cycle includes thecompressor 206, the main condenser 207, the sub-condenser 205, a liquidtank 208, an expansion valve 209 as a pressure-reducing means or device,the evaporator 204, and an accumulator 210 which are fluidly connectedwith each other a piping or lines 212 for the refrigerant. It will beunderstood that the refrigerant is sealingly filled in the refrigerationcycle.

The liquid tank 208 functions to separate the gas state refrigerant andthe liquid state refrigerant and store therein the liquid staterefrigerant so as to discharge only the liquid state refrigerant to theexpansion valve 209. This liquid tank 208 also functions to separate airand to remove water and foreign matters. The expansion valve 209functions to make an expansion of the liquid state refrigerant under areduced pressure thereby changing the liquid state refrigerant into themist state refrigerant which is low in temperature and pressure, andfunctions to automatically control the flow amount of the refrigerant inresponse to the temperature at the outlet of the evaporator 204 (in caseof the expansion valve 209 being of the temperature-responsive type).The accumulator 210 functions to store therein the excess refrigerantand to separate the gas state refrigerant and the liquid staterefrigerant so as to return the gas state refrigerant to the compressor206. The accumulator 110 is relatively large in volume, so that even ifthe refrigerant is returned in the liquid state to the accumulator 210,the refrigerant is evaporated to be returned to the compressor 206,thereby preventing the compressor 206 from breakage due to compressionof liquid.

It will be understood that the liquid tank 208 and the accumulator 210are partly common in function to each other, and therefore both are notnecessarily required. In this regard, according to the presentinvention, it is preferable to provide at least the accumulator 210 inorder to accomplish recovery of the refrigerant (as the liquid staterefrigerant) from the outlet of the main condenser 207. Accordingly,both the liquid tank 208 and the accumulator 210 are provided, forexample, in a case such as this embodiment in which thetemperature-responsive expansion valve 209 is used as thepressure-reducing means. Otherwise, only the accumulator 210 may beprovided omitting the liquid tank 208 in case that an electromagneticvalve (not shown) having an orifice is used in place of thetemperature-responsive expansion valve 209, in which the electromagneticvalve is a flow amount changeover valve of the type wherein position ofa valve member is changed to take either one of a fully opened state anda partly opened state of the valve.

The reference numerals 216, 217, 218 designate respectively check valvesto prevent the refrigerant from flowing in a reverse direction. Thereference numeral 219 designates a condenser fan for blowing air to themain condenser 207 so as to cool the main condenser 207.

In this embodiment, a three-way valve 220 is provided between thedischarge outlet of the compressor 206 and the inlet of the maincondenser 207 in order to accomplish the change-over for the condensersto be functioned during the heating operation and the refrigerationoperation of the air conditioning system A. That is, the three-way valve220 functions as flow passage change-over means or device for changingover the flow passage of the refrigerant from one circuit to anothercircuit. More specifically, the three-way valve 220 has one inlet portand two outlet ports for the refrigerant. The inlet port is connected tothe discharge side of the compressor 206, while the two outlet ports areconnected respectively to the inlet of the main condenser 207 and theoutlet of the main condenser 207 through a bypass passage or pipe 213.By selecting one of the two outlet ports to be communicated with theinlet port, flow of the refrigerant discharged from the compressor 206is changed over from a refrigeration cycle in which the refrigerant isdirected to the main condenser 207 to a heating cycle in which therefrigerant is directly directed to the sub-condenser 205 through thebypass passage 213 and vice versa.

The reference characters D1, D2 designate flow directions of therefrigerant respectively during the refrigeration operation and theheating operation of the air conditioning system A. The referencecharacter D3 designates a refrigerant recovering direction (i.e., a flowdirection of the refrigerant to be recovered).

During the refrigeration operation of the air conditioning system A,under the operation of the three-way valve 220, the refrigerantdischarged from the compressor 206 is introduced into the main condenser207. More specifically, the refrigerant discharged from the compressor206 flows through the three-way valve 220, the main condenser 207, thesub-condenser 205, the liquid tank 208, the expansion valve 209, theevaporator 204, and the accumulator 210 in the order mentioned and thenreturns to the compressor 206, thus forming the refrigeration cycle. Bythis, in the evaporator 204, heat exchange is made between the liquidstate refrigerant and air in such a manner that air passing through aspace around the refrigerant passage is cooled with the liquid staterefrigerant which is evaporating, thus refrigerating the passengercompartment. In the main condenser 207, the refrigerant releases to theoutside the heat taken in by the evaporator 204 under heat exchangebetween the refrigerant and the outside air, thereby cooling andcondensing the gas state refrigerant to obtain the liquid staterefrigerant. At this time, the sub-condenser 205 hardly functions as aheat exchanger.

During heating operation of the air conditioning system A, underoperation of the three-way valve 220, the refrigerant discharged fromthe compressor 206 is introduced directly to the sub-condenser 205through the bypass passage 213. More specifically, the refrigerantdischarged from the compressor 206 flows through the three-way valve220, the bypass passage 213, the sub-condenser 205, the liquid tank 208,the expansion valve 209, the evaporator 204, and the accumulator 2 10 inthe order mentioned and then returns to the compressor 206, withoutusing the main condenser 207, thereby forming the heating cycle. Bythis, the high temperature and pressure gas state refrigerant which hasbeen discharged from the compressor 206 and bypasses the main condenser207 is condensed and liquefied in the sub-condenser 205 to release heat,so that air cooled by the evaporator 204 is heated and blown to thepassenger compartment thereby heating the passenger compartment. At thistime, the evaporator 204 cools and dehumidifies the air taken in, thusachieving a heating operation with dehumidification.

The air conditioning system A of this embodiment comprises a refrigerantrecovery system R for returning the refrigerant staying in the maincondenser 207 to the suction side of the compressor 206 during theheating operation of the air conditioning system A. The refrigerantrecovery system R is arranged to recover the refrigerant from the outletof the main condenser 207. More specifically, the refrigerant recoverysystem R includes a refrigerant recovery passage or pipe (line) 230which is connected at its one end to the outlet piping of the maincondenser 207 through a three-way connector (not identified), so thatthe refrigerant recovery passage 230 is formed branched. Anelectromagnetic valve 231 is disposed in this refrigerant recoverypassage 230 to be opened or closed. The other end of the refrigerantrecovery passage 230 is connected to the inlet of the accumulator 2 10through a three-way connector (not identified), thus forming a circuitfor recovering the refrigerant. The electromagnetic valve 231 isprovided for the purpose of preventing the refrigerant flowing out ofthe main condenser 207 from flowing into refrigerant recovery passage 30during the refrigeration operation.

By thus recovering the refrigerant from the main condenser 207, therefrigerant can be recovered in its liquid state since the liquid staterefrigerant is accumulating at the bottom portion of the main condenser207 as shown in FIG. 9. As a result, the time required for recoveringthe refrigerant is largely shortened while the amount of the refrigerantto be recovered can be largely increased as compared with a case inwhich the refrigerant is recovered in its gas state. This has beenexperimentally confirmed as follows: For example, when the temperatureof the outside air was −20° C., not less that 300 g (the generally wholeamount of the refrigerant in the main condenser 207) of the refrigerantcould be recovered within 90 seconds. Additionally, no reverse flow ofthe refrigerant could not be found even upon continuation of therecovery of the refrigerant.

Upon taking the above experimental result into consideration, theopen-dose control of the electromagnetic valve 231 is carried out asfollows: The electromagnetic valve 231 is switched ON to be opened for apredetermined time (for example, 90 seconds) since the initiation of theheating operation of the air conditioning system A so as to allow therefrigerant to flow through the refrigerant recovering passage 230. Uponlapse of the predetermined time (90 seconds) or upon completion ofrecovering the refrigerant, the electromagnetic valve 231 is switchedOFF to block the refrigerant recovering passage 230 so as to stop theflow of the refrigerant through the refrigerant recovering passage 230.Additionally, during the refrigeration operation of the air conditioningsystem A, the electromagnetic valve 231 is always switched OFF to blockthe refrigerant recovery passage 230. It will be understood that theabove predetermined time for recovering the refrigerant is not limitedto 90 seconds, and therefore may be set at a suitable value which isrequired for obtaining a necessary recovering amount of the refrigerantfor each air conditioning system.

According to this embodiment, since recovering the liquid staterefrigerant is accomplished from the outlet of the main condenser 207, alarge amount of refrigerant can be recovered for a short time withoutoccurrence of reverse flow of the refrigerant to the main condenser 207,thereby shortening the refrigerant recovering time (a time for which theelectromagnetic valve 231 is switched ON). Additionally, the necessaryand sufficient amount of the refrigerant stayed in the main condenser207 can be recovered within the refrigerant recovering time, andtherefore an appropriate amount of the refrigerant can be alwaysmaintained in the heating cycle during the heating operation of the airconditioning system A. This solves the problems of a degraded heatingperformance and a degraded lubricating characteristics occurred in theheating operation under a too-small amount condition of the refrigerant,thus obtaining the same performance even upon repeated operations of theair conditioning system A.

FIG. 6 illustrates a modified example of the third embodiment of the airconditioning system A according to the present invention. This modifiedexample is similar to the third embodiment with the exception that apilot pressure differential-operated electromagnetic valve 231 a is usedin place of the electromagnetic valve 231 which is arranged to controlopposite flows of the refrigerant therethrough. The pilot pressuredifferential-operated electromagnetic valve 231 a is low in cost andless in electric power consumption as compared with the electromagneticvalve 231 which is directly operated to allow also the reverse flow ofthe refrigerant therethrough, and therefore the electromagnetic valve231 a is particularly preferably used in an air conditioning systemmounted on an electric vehicle.

The pilot pressure differential-operated electromagnetic valve 231 a isadapted to be able to control flow of the refrigerant only in onedirection, and therefore it is disposed to allow the refrigerant to flowin the refrigerant recovery direction (i.e., the direction of flow ofthe refrigerant to be recovered) indicated by the arrows D3. The pilotpressure differential-operated electromagnetic valve 231 a itself isknown, and therefore explanation of the structure of the electromagneticvalve 231 a is omitted for the purpose of simplicity of illustration.

The refrigerant recovery system R2 of this example includes therefrigerant recovery passage 230 connecting the outlet of the maincondenser 207 and the suction side of the compressor 206 and operates asfollows: When the internal pressure (saturated pressure) of the maincondenser 207 is higher than the suction pressure of the compressor 206at starting of the heating operation of the air conditioning system A,the refrigerant stayed in the main condenser 207 is returned in itsliquid state from the outlet of the main condenser 207 to the suctionside of the compressor 206 through the refrigerant recovery passage 230so as to be recovered to the heating cycle. Here, since the pilotpressure differential-operated electromagnetic valve 231 a is used as avalve disposed in the refrigerant recovery passage 230, there is thepossibility of the following shortcomings arising: When the temperatureof the outside air is low (for example, at −20° C.) and the temperaturewithin the passenger compartment is about 20° C. under a condition inwhich the electromagnetic valve 231 a in the refrigerant recoverypassage 230 is closed (switched OFF) after completion of recovery of therefrigerant, the internal pressure (saturated pressure) of the maincondenser 207 may be lowered below the suction pressure of thecompressor. In this case, there is the possibility of the refrigerantflowing in the reverse direction from the suction side of the compressor206 to the side of the main condenser 207 under the action of a reversepressure differential to the electromagnetic valve 231 a so as to allowthe reverse flow of the refrigerant through the electromagnetic valve231 a.

In view of this, according to this example, a check valve 232 isdisposed in the refrigerant recovery passage 230 and located downstreamof the pilot pressure differential-operated electromagnetic valve 231 arelative to flow of the refrigerant recovery direction D3. Specifically,the check valve 232 is disposed between the pilot pressuredifferential-operated electromagnetic valve 231 a and the suction side(more specifically, at the inlet of the accumulator 210) of thecompressor 206 and is so directed as to block flow of the refrigerant ina direction from the suction side of the compressor 206 to the maincondenser 207. By this, even if the refrigerant recovery system R2 usingthe pilot pressure differential-operated electromagnetic valve 231 a isput into a condition where the reverse flow of the refrigerant occursthrough the refrigerant recovery passage 230, the reverse flow isprevented from occurrence under the action of the check valve 232,thereby preventing the refrigerant from accumulating in the maincondenser 207 owing to leaking of the refrigerant from the suction sideof the compressor 206 to the side of the main condenser 207 during theheating operation of the air conditioning system A. This maintains asuitable amount of the refrigerant in the heating cycle during theheating operation of the air conditioning system A.

The other arrangements and operations are the same as those in the thirdembodiment air conditioning system A, and therefore explanation of thoseis omitted for the purpose of simplicity of illustration.

FIG. 7 illustrates another modified example of the third embodiment airconditioning system A according to the present invention. This modifiedexample is similar to the example of FIG. 6 with the exception that twoelectromagnetic valves 233, 234 are disposed in place of the three-wayvalve 220 as the flow passage change-over means. For example, the twoelectromagnetic valves 233, 234 are respectively the pilot pressuredifferential-operated electromagnetic valves since the flow directionsin the lines in which the electromagnetic valves 233, 234 are disposedare always constant, thereby suppressing a cost increase at the minimumvalue.

In this example, during the refrigeration operation of the airconditioning system A, the electromagnetic valve 233 disposed in theinlet piping of the main condenser 207 is opened (switched ON) while theelectromagnetic valve 234 disposed in the bypass passage 213 is closed(switched OFF), so that the refrigerant discharged from the compressor206 is introduced into the main condenser 207 thereby forming therefrigeration cycle. In contrast, during the heating operation of theair conditioning system A, the electromagnetic valve 233 disposed in theinlet piping of the main condenser 207 is closed (switched OFF) whilethe electromagnetic valve 234 disposed in the bypass passage 213 isopened (switched ON), so that the refrigerant discharged from thecompressor 206 is introduced directly into the sub-condenser 205 throughthe bypass passage 213 thereby forming the heating cycle.

The other arrangements and operations are the same as those in themodified example of FIG. 6, and therefore explanation of those isomitted for the purpose of simplicity of illustration.

FIG. 8 illustrates a further modified example of the third embodiment ofthe air conditioning system A according to the present invention, whichis similar to the third embodiment shown in FIG. 5 with the exceptionthat a sub-evaporator or exterior evaporator (located outside thepassenger compartment) 235 is disposed in a low pressure-siderefrigerant passage between the suction side (more specifically, theinlet of the accumulator 210 and the outlet of the evaporator 204 inorder to raise the heating performance of the heat pump system of theair conditioning system A. The sub-evaporator 235 functions to heat therefrigerant flowing through the sub-evaporator under heat exchangebetween the refrigerant and the engine coolant flowing through thesub-evaporator 235, thus accomplishing heat exchange between hot waterand the refrigerant. The reference numeral 236 designates a water valvefor allowing the engine coolant to flow through the sub-evaporator 235.

By virtue of the sub-evaporator 235, even if the engine coolant is lowin temperature and in a condition to be difficult to be immediately usedfor heating the passenger compartment under heat exchange between it andair, the refrigerant effectively takes in heat retained in the enginecoolant and is heated under heat exchange between it and the enginecoolant in the sub-evaporator 235, in which the enthalpy of therefrigerant is increased. Thereafter, the refrigerant returns to thecompressor 206 and then again compressed to be increased in pressure bythe compressor 206. The refrigerant discharged from the compressor 206becomes further high in pressure and is supplied to the sub-condenser205. As a result, the heat releasing performance of the sub-condenser205 is increased, so that air subjected to heat exchange in thesub-condenser 205 becomes further high in temperature. Accordingly, theair conditioning system A exhibits a further high heating performancewhile being improved in the instant or quick heating ability for thepassenger compartment.

In case that the expansion valve 209 is of the temperature responsivetype, it is preferable that a temperature detecting section (not shown)of the expansion valve 209 is disposed at the outlet of thesub-evaporator 235. By this, the flow amount of the refrigerant iscontrolled in response to the temperature of the refrigerant which hasbeen heated by the sub-evaporator, and therefore a large amount of therefrigerant can circulate during operation of the sub-evaporator 35thereby promoting a further improvement in the heating performance ofthe air conditioning system A.

The other arrangements and operations are the same as those in the thirdembodiment of FIG. 1, and therefore explanation of those is omitted forthe purpose of simplicity of illustration.

According to the third embodiment air conditioning system A, therefrigerant can be recovered in its liquid state from the outlet of theexterior condenser during the heating operation of the air conditioningsystem. Accordingly, a large amount of the refrigerant can be recoveredfor a short time without causing a reverse flow of the refrigerant tothe exterior condenser. The amount of the refrigerant within the heatingcycle can be always maintained at a suitable level during the heatingoperation of the air conditioning system. This solves the problems oflowering the heating performance due to the heating operating under arefrigerant-shortage condition and of lowering a lubricating ability,thereby improving the performance and reliability of the airconditioning system.

What is claimed is:
 1. A heat pump type air conditioning system for anautomotive vehicle, comprising: a first unit including a heater corethrough which an engine coolant of an engine flows, and a first heatexchanger which forms part of a refrigeration cycle including acompressor and a first condenser, a refrigerant circulating in saidrefrigeration cycle; a second unit including a second condenser and asecond heat exchanger which are fluidly connected in parallel with saidfirst heat exchanger; a valve fluidly connected in series with saidsecond condenser and disposed such that a part of the refrigerant isintroduced through said valve into said second condenser and said secondheat exchanger; a sub-heat exchanger disposed outside said first andsecond units and fluidly connected in series with said second heatexchanger, the refrigerant flowing from said second heat exchanger beingintroduced into said sub-heat exchanger to be heated by a part of theengine coolant, the refrigerant discharged from said sub-heat exchangerbeing returned to the said compressor; an electromagnetic clutch throughwhich said compressor is drivably connectable with the engine, saidelectromagnetic clutch being engaged to establish a driving connectionbetween the compressor so as to operate said compressor and disengagedto cut the driving connection so as to make said compressor inoperative;and a control device operatively connected to said electromagneticclutch for controlling said electromagnetic clutch to be disengageablein accordance with a temperature within said air conditioning system. 2.A heat pump type air conditioning system as claimed in claim 1, whereinsaid control device is adapted to cause said electromagnetic clutch tobe disengaged when a temperature of air taken in said second unitreaches a predetermined level.